S-93A46A/56A/66A

Seiko Instruments Inc.

11

4. Writing (WRITE, ERASE, WRAL, ERAL)

A write operation includes four write instructions: data write (WRITE), data erase (ERASE), chip write

(WRAL), and chip erase (ERAL).

A write instruction (WRITE, ERASE, WRAL, ERAL) starts a write operation to the memory cell when a

low level is input to CS after a specified number of clocks have been input. The SK and DI inputs are

invalid during the write period, so do not input an instruction.

Input an instruction while the output status of the DO pin is high or high impedance (Hi-Z).

A write operation is valid only in program enable mode (refer to “5. Write Enable (EWEN) and Write

Disable (EWDS)

”).

4.1 Verify Operation

so if the completion of the write operation is recognized, the write cycle can be minimized. A

sequential operation to confirm the status of a write operation is called a verify operation.

(1) Operation

After the write operation has started (CS

= low), the status of the write operation can be verified by

confirming the output status of the DO pin by inputting a high level to CS again. This sequence is

called a verify operation, and the period that a high level is input to the CS pin after the write

operation has started is called the verify operation period.

The relationship between the output status of the DO pin and the write operation during the verify

operation period is as follows.

• DO pin = low: Writing in progress (busy)

• DO pin = high:Writing completed (ready)

(2) Operation Example

There are two methods to perform a verify operation: Waiting for a change in the output status of

the DO pin while keeping CS high, or suspending the verify operation (CS

= low) once and then

performing it again to verify the output status of the DO pin. The latter method allows the CPU to

perform other processing during the wait period, allowing an efficient system to be designed.

Caution 1. Input a low level to the DI pin during a verify operation.

2. If a high level is input to the DI pin at the rise of SK when the output status of the

DO pin is high, the S-93A66A latches the instruction assuming that a start bit has

been input. In this case, note that the DO pin immediately enters a high-impedance

(Hi-Z) state.